The present invention relates to a belt drive comprising a toothed belt and a toothed pulley, with the toothed belt, which is made of plastic or some other extrudable material, containing an inextensible reinforcing insert that is embedded in the belt body thereof and also being provided with guide rib means that extends in a longitudinal direction of the toothed belt and traverses ribs of the belt, with the guide rib means, during rotation of the toothed belt about the toothed pulley, engaging in annular groove-like recess means disposed on the periphery of the toothed pulley, and with the guide rib means, to increase their flexibility, being provided with notches in the vicinity of grooves of the toothed belt.
Normally, as toothed belts rotate about a toothed pulley, they are guided on the sides between two lateral flanges of the toothed pulley. However, there are also toothed belt drives, for example where the belt is used as a transport member in conveying units, where flanges of a toothed pulley cannot project laterally beyond the toothed belt. For this purpose, see for example U.S. Pat. No. 2,770,977, a self-guiding toothed belt is known that is provided on its toothed side with one or more strip-like guide ribs that extend in the longitudinal direction of the belt; these guide ribs engage in conforming annular grooves on the toothed peripheral surface of the toothed pulley in order thereby to laterally guide the toothed belt even where the toothed pulley has no flanges. Unfortunately, due to the presence of the strip-like guide ribs, the force-transfer surface at the sides of the toothed ribs is reduced, so that in order to be able to transfer the same drive power as in the case without the guide ribs, the toothed belt has to be wider. However, this also increases the noise made by the belt as it rotates about the toothed pulley.
Starting from the aforementioned toothed belt construction having a guide rib for self-guidance on a toothed pulley that has no flange, it is an object of the present invention to provide for a quieter operation of the toothed belt about the toothed pulley.